1. Field of the Invention
This invention relates to an electronic part mounting apparatus which attracts a very small electronic part or chip thereto and places it at a predetermined location on an electronic circuit board or the like to effect automatic mounting of the electronic part, and more particularly to an original orientation restoring mechanism and an original orientation restoration detecting mechanism in an electronic part mounting apparatus of the type mentioned for returning the angular position of a nozzle provided for attracting a chip thereto to a predetermined original angular position.
2. Description of the Prior Art
Various electronic part mounting apparatus for mounting a chip on an electronic circuit board are conventionally known and disclosed, for example, in Japanese Patent Laid-Open Application No. 62-13100 and Japanese Patent Laid-Open Application No. 1-157600.
An outline of such conventional electronic part mounting apparatus will be described with reference to FIGS. 6 to 9. A part cassette or electronic part taking out apparatus is provided on a chip supplying station 3 and strips an upper face tape from a mount tape 2 of a double tape to expose a chip enclosed in the double tape on the mount tape 2. Chips 1a and 1b shown in FIG. 6 are in such an exposed condition.
A position P1 on the chip supplying station 3 is a chip attracting position at which a nozzle 7 provided below a rotary head 4 of a part moving mechanism attracts thereto by vacuum the chip 1b exposed above the mount tape 2. The rotary head 4 having the chip 1b attracted thereto is rotated, as an index table 10 is rotated around a support shaft 11, to a displacement detecting position P2 at which displacement of the chip is detected by an optical sensor 17.
The displacement here signifies displacement of such a chip as the chip 1a which is inclined from its regular position when the nozzle 7 attracts the chip 1b thereto by vacuum at the position P1. Since a chip which remains in an inclined position cannot be placed regularly onto a circuit board 5 on a bed 6 which is movable in perpendicular X-Y directions, displacement of a chip is detected by means of the visual sensor 17 in order to correct such displacement at a position P3. A rotary head rotating adjusting mechanism 15 is provided for such correction.
The rotary head 4 places the chip attracted to the nozzle 7 thereof at a position P4. The circuit board 5 is carried on the bed 6, and the bed 6 moves the circuit board 5 to define a position at which the chip is to be dropped from the nozzle 7 of the rotary head 4.
An original orientation restoration of the rotary head 4 is performed at a position P5. In particular, while the chip was rotated by an angle .theta. at the position P3 to offset the displacement described above, the nozzle 7 is rotated back by an angle equal to the rotational angle .theta. to restore its original position in order to allow the nozzle 7 to attract a next chip at the position P1. For the original orientation restoration, an original orientation restoring driving mechanism 16 and an original orientation restoring gear 14 are provided. The original orientation restoring gear 14 is held out of engagement with the gear 12 when the index table 10 is rotation, but when an original orientation restoring operation is required, the original orientation restoring gear 14 is rocked toward the rotary head 4 by the original orientation restoring driving mechanism 16 and engaged with the rotary head rotation adjusting gear 13.
It is to be noted that such original orientation restoring operation is performed, where the nozzle 7 has two nozzle holes 7a and 7b at an end thereof as shown in FIGS. 10A and 10B, selectively for a 90-degree position original orientation restoring operation (FIG. 10A) or for a 0-degree position original orientation restoring operation (FIG. 10B) so that the chip 1 may be attracted in a most suitable condition depending upon orientation of a chip 1 on the tape 2.
Meanwhile, in order to detect such original orientation restoration, a pair of nozzle original orientation select pins 8a and 8b are provided on the nozzle 7 as shown in FIG. 7, and turning motion of the select pin 8a or 8b is detected by an original orientation restoration detecting mechanism (not shown) provided separately from the original orientation restoring driving mechanism 16. The original orientation restoration detecting mechanism is a kind of limit switch and detects that the nozzle 7 has returned to a predetermined origin position when a select pin 8a or 8b is engaged with the limit switch, and when such original orientation restoration is detected, the original orientation restoration detecting mechanism stops operation of the original orientation restoring gear 14.
The conventional original orientation restoring mechanism employs the original orientation restoring gear 14 which is selectively engaged with the gear 12 of the rotary head 4. However, there is a problem that much time is required to smoothly effect meshing engagement between the gear 12 and the original orientation restoring gear 14. From a point of view of an operation speed of the entire electronic part mounting apparatus, a demand for such a high speed operation that an original orientation restoring operation must be completed within 0.1 to 0.2 seconds or so is increased, and a problem is encountered that such conventional meshing engaging method cannot satisfy such high speed original orientation restoring operation.
Further, while the conventional original orientation restoration detecting mechanism is rocked, upon an original orientation restoring operation, toward the nozzle 7, in a manner similar to the original orientation restoring gear 14, since it is driven by a moving mechanism separate from the original orientation restoring driving mechanism 16, such a driving source as a solenoid or an air cylinder is required separately as the moving mechanism. Further, since the original orientation restoration detecting mechanism requires a separate space also for the rocking motion, then the construction of the entire electronic part mounting apparatus becomes great, and further it is difficult to mount the driving source and the original orientation restoration detecting section in a situation wherein miniaturization is required.